Apparatus for drying pulverant materials

ABSTRACT

Apparatus for drying pulverant materials through continuous fluidization which comprises a means for keeping the gas pressure in the first drying chamber at a lowest level and increasing the gas pressure gradually in the ensuring chambers until it reaches a maximum in the last drying chamber, while, on the contrary, a means for maintaining the pulverant material layer at the highest level in the first drying chamber and decreasing the height gradually in the ensuing chambers until it reaches a minimum.

United States Patent Jlyuichi Nara 2-7-8 Higmhi-Ooi Shinagawa-Ku, Tokyo, Japan June 1 l, 1969 Aug. 17, 1971 June 19, 1968 Japan inventor Appl. No. Filed Patented Priority APPARATUS FOR DRYING PULVERANT MATERIALS 1 Claim, 2 Drawing Figs.

us. (:1 34/51 A rm. Cl F26b mm ma 0: Search 34/57 A, 57, 1o; 23/288.35; 203/21 A References Cited UNITED STATES PATENTS 4/1947 Arveson 2,502,953 4/1950 Jahnig 34/57 X 2,529,366 11/1950 Bauer 34/10 UX 2,629,938 3/1953 Montgomery.. 34/10 3,212,197 10/1965 Crawford 34/57 A X 3,360,867 1/1968 Sanderson 34/10 FOREIGN PATENTS 140,132 2/1951 Australia 34/10 1,345,666 11/1963 France 34/57 A Primary Examiner- Frederick L. Matteson Assistant Examiner-Robert A. Dua Attorney-George B. Oujevolk ABSTRACT: Apparatus for drying pulverant materials through continuous fluidization which comprises a means for keeping the gas pressure in the first drying chamber at a lowest level and increasing the gas pressure gradually in the ensuring chambers until it reaches a maximum in the last drying chamber, while, on the contrary, a means for maintaining the pulverant material layer at the highest level in the first drying chamber and decreasing the height gradually in the ensuing chambers until it reaches a minimum.

APPARATUS FOR DRYING PULVERANT MATERIALS SUMMARY OF THE INVENTION This invention relates to an apparatus for drying pulverant materials by arranging a plurality of drying chambers in a row and supplying and fluidizing a pulverant material therethrough.

The present invention has as its object to provide a high efficient drying apparatus for pulverant materials in which a plurality of drying chambers are arranged in a horizontal series with a common perforated plate, and hot gas conditions in the drying chambers are varied according to the degrees of dryness of the pulverant material in the individual chambers so as to ensure a good drying efficiency, and the dusts formed in these chambers are supplied back to the portion of the pulverant material that exhibits the highest degree of wetness so as to separate the damp material into particles, enhance the drying efficiency and diminish the rate of dusting successively.

In order to realize the above object the present invention provides an apparatus of multichamber, continuous-flow type for drying pulverant materials comprising a plurality of drying chambers arranged with a common perforated plate, said chambers being communicated in series with one another through spaces provided between the lower ends of the walls partitioning adjoining chambers and the common perforated plate, the first drying chamber having an inlet port on the top thereof which is provided with a nonreturn valve for the supply of damp pulverant material, a weir plate slidable upward and downward which is provided at the exit end of the last drying chamber, said last chamber being also formed with exit ports for dried pulverant material through which the material can overflow and underflow the weir plate respectively, air shutoff-type powder dischargers provided at the exit ports for the pulverant material, hot gas communicating chambers for communicating hot gas conditioners to the underside of the perforated plate in common with the individual drying chambers, heat exchangers located in the-individual chambers and which selectively use steam or hot water, damp gas discharge pipes provided on top of the individual chambers and which are equipped with pressure controlling valves, one for each pipe, and cyclone collectors communicated to said discharge pipes, said cyclone collectors having gas discharge ports respectively in communication with said hot gas conditioners.

The present invention also provides for an arrangement for drying pulverant materials through continuous fluidization, which comprises, in operating the apparatus above defined, keeping the gas pressure in the first drying chamber at a lowest level and increasing the gas pressure gradually in the ensuing chambers until it reaches a maximum in the last drying chamber, while, on the contrary, maintaining the pulverant material layer at the highest level in the first drying chamber and decreasing the height gradually in the ensuing chambers until it reaches a minimum.

The invention will now be described in further detail in conjunction with the accompanying drawings showing an embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side view of a multichamber, continuous-flow-type apparatus for drying pulverant materials em bodying the invention; and

FIG. 2 is a transverse sectional view taken along the line A-A of FIG. 2.

DETAIL OF THE INVENTION In the apparatus shown, a plurality of drying chambers generally indicated at I, II, and III are arranged with a common perforated plate 1. The chambers are communicated in series with one another through spaces 3 provided between the lower ends of the walls 2 partitioning adjoining chambers and the common perforated plate 1; The first drying chamber has an inlet port 4 on the top thereof for the supply of damp pulverant material (and which is equipped, for example, with a screw feeder or rotary valve). At the rear end of the last drying chamber there are provided a weir plate 5 which is slidable upward and downward, and also exit ports 6 and 6 for dried pulverant material through which the material can overflow and underflow the weir plate respectively. Air shutoff-type powder dischargers 7 and 7' are provided at the exit ports 6 and 6' for the pulverant material. Hot gas communicating chambers 9, 9 and 9" communicate the hot gas conditioners 8, 8' and 8" to the underside of the perforated plate 1 in common with the individual drying chambers I, II and III. Heat exchangers l0, l0 and 10 are located in the individual chambers I, II and III and pennit selective use of steam or hot water as the medium. Exhaust pipes l2, l2 and 12" for humidified gas are provided on top of the individual chambers I, II and III and are equipped with pressure controlling valves 1 l, 11' and l 1", respectively. Cyclone collectors 13 and 13' are communicated to said discharge pipes and have gas discharge ports respectively in communication with said hot gas conditioners 8, 8' and 8".

Reference numerals 14 and 14' indicate dehumidifiers for wet pulverant material. Numeral 15 indicates a screw feeder, and 16 indicates a powder diffuser. 1

The hot gas conditions 8, 8' and 8" as used in the apparatus shown are of the well-known type capable of controlling the dryness, temperature and blast pressure of the hot gas as desired, for example Peabody scrubber.

The operation of the apparatus according to the present invention will now be described.

This apparatus can be employed for the drying of pulverant organic materials such as synthetic resins and pulverant inorganic materials such as ammonium sulfate and potassium chloride which contain various organic solvents or water either single or in mixture.

In operating the apparatus of the invention, wet pulverant material is fed, through or not through the dehumidifiers l4 and 14, into the first drying chamber I by means of the screw feeder 15 or other air shutoff-type powder feeder. The use of the powder diffuser 16 is beneficial in that it promotes the separation of the pulverant material into particles. In the individual chambers I, II and III, hot gas such as air or nitrogen gas is supplied to the hot gas communicating chambers 9, 9' and 9" after the adjustments of the temperature, dryness, pressure, etc. The pulverant material on the perforated plate 1 is fluidized by the hot gas and is dried by heat exchange through contact with the heat exchangers l0, l0 and 10''. Said heat exchangers are such conventional type as flow heat medium into pipe, At this time, the pulverant material moves gradually from the drying chamber I to the ensuing drying chambers II and III through the spaces provided between the lower ends of the partition walls 2 or the chambers and the perforated plate 1. Finally the pulverant material is overflown beyond the upper edge of the weir plate 5 at the rear end of the last drying chamber and is discharged through the exit port equipped with the rotary valve 7( Also the pulverant material agglomerated to small lumps is discharged from under the lower edge of the weir plate 5 and through the exit port equipped with a rotary valve 7'. Without this exit port the small lumps would fail to overflow the weir plate and would be accumulated in the corner of the last drying chamber.

In the present apparatus, simultaneously with the operation above described, humidified gas is exhausted together with floating dust through exhaust pipes 12, 12 and I2" provided on top of the individual chambers I, II and III, into the cyclone collectors 13, 13 and 13''. From these cyclone collectors the pulverant material is brought back into the damp pulverant material in the first drying chamber I where it decreases the average wetness of the material being fed while, at the same time, the floating dust deposits on the damp material, thus serving to avoid the agglomeration of the wet particles and facilitate the drying.

On the other hand, the humidified gas discharged from the cyclone collectors 13, l3 and 13' is recycled to the hot gas conditioners 8, 8 and 8" and is conditioned to meet the individual requirements of the drying chambers and is reused for the fluidization of the pulverant material.

In the operation of the apparatus the gas pressures in the respective chambers are regulated by the hot gas conditions 8, 8' and 8" and also by the valves 11, 11' and 11', so that the pressure in the last chamber is kept at a maximum and the pressure in the first chamber is kept at a minimum, while the height of the fluidized pulverant material layer is conversely controlled so that the level in the first chamber is kept high and then gradually lowered. Consequently, the mass of pulverant material moves ahead smoothly by its own head against the counter pressure, and thus the advance of the.hot gas humidified by a frontal drying chamber towards the rear drying chambers is avoided and the respective chambers are enabled to carry out the tasks efficiently.

It is noted in this connection that although a very damp pulverant material may be dried by high-humidity gas a less damp pulverant material should be dried by low-humidity gas for both physical and economical reasons,

In this case, the flow of high-himidity gas into the low humidity region not merely affects the dryness of the pulverant material adversely but, in addition, gives an unfavorable effect upon the cooling dehumidifiers in the recycling system. Some leakage of the low-humidity gas into the high-humitity region is not objectionable in the least.

With the construction above described, the apparatus of the present invention when operated in the manner described can efficiently dry up pulverant materials at a great advantage.

I claim:

1. An apparatus for drying pulverant material comprising in combination:

a. at least first and second vertical drying chambers arranged in series with at least one common partition wall (2) including an inlet port (4) to said first chamber at the top thereof, an exit port (6) to said second chamber;

b. a common perforated plate (1) at the bottom of said chambers; I

c. at least one communication space (3) between said chambers at the lower vertical end of said common wall;

d. hot gas communication chambers (9) under said perforated plate (1) in each chamber and hot gas conditions (8) connected to said gas communication chambers; I

e. heat exchangers in each chamber including hot fluid supply means therein;

f. damp gas discharge pipes at the top of each chamber including pressure controlling valves (12); and

I g. cyclone collectors (13) disposed over each chamber fed by said discharge pipes, said cyclone collectors having gas discharge ports in communication with said hot gas conditions, whereby, in operating the above defined apparatus, the gas pressure in the first drying chamber is kept at a low level and the gas pressure increases gradually in the ensuing chambers until it reaches a maximum in the last drying chamber, while, on the contrary, the pulverant material layer is maintained at the highest level in the first drying chamber and the height is decreased gradually in the ensuing chambers until it reaches a minimum. 

1. An apparatus for drying pulverant material comprising in combination: a. at least first and second vertical drying chambers arranged in series with at least one common partition wall (2) including an inlet port (4) to said first chamber at the top thereof, an exit port (6) to said second chamber; b. a common perforated plate (1) at the bottom of said chambers; c. at least one communication space (3) between said chambers at the lower vertical end of said common wall; d. hot gas communication chambers (9) under said perforated plate (1) in each chamber and hot gas conditions (8) connected to said gas communication chambers; e. heat exchangers in each chamber including hot fluid supply means therein; f. damp gas discharge pipes at the top of each chamber including pressure controlling valves (12); and g. cyclone collectors (13) disposed over each chamber Fed by said discharge pipes, said cyclone collectors having gas discharge ports in communication with said hot gas conditions, whereby, in operating the above defined apparatus, the gas pressure in the first drying chamber is kept at a low level and the gas pressure increases gradually in the ensuing chambers until it reaches a maximum in the last drying chamber, while, on the contrary, the pulverant material layer is maintained at the highest level in the first drying chamber and the height is decreased gradually in the ensuing chambers until it reaches a minimum. 